Every time a fish school emerges in the Ocean (only Rough or Swell) near player, there is a 7.5% chance that Gnarwail will spawn. When killed, the Gnarwail drops four Raw Fish and one Gnarwail Horn if its horn is not destroyed.
When attacked, they will drill Boats with their Horn, damaging them and creating a leak. When drilling, the Horn can be attacked and destroyed without killing the Gnarwail, dropping one Gnarwail Horn. If a Gnarwail doesn't have a horn, it will attack by jumping into their targets, creating Waves in the ocean. They attack anything that isn't located on a boat with their jump attack only.
Gnarwails can be befriended by giving them Meats. They follow for 25 per day for up to 2.5 days. Follower Gnarwails will regularly toss Items floating in the Ocean towards the player.